Efforts to improve photovoltaic (PV) devices, particularly those devices that are integrated into building structures (e.g. photovoltaic sheathing elements, spacer pieces, edge pieces), to be used successfully, should satisfy a number of criteria. The PV device and the array as installed should be durable (e.g. long lasting, sealed against moisture and other environmental conditions) and protected from mechanical abuse over the desired lifetime of the product, preferably at least 10 years, more preferably at least 25 years. The device should be easily installed into the array of devices (e.g. installation similar to conventional roofing shingles or exterior wall coverings) or replaced (e.g. if damaged). It also, should be designed to prevent, as much as possible, water from getting under the device and to the building surface that the device is affixed to.
To make this full package desirable to the consumer, and to gain wide acceptance in the marketplace, the system should be inexpensive to build and install. This may help facilitate lower generated cost of energy, making PV technology more competitive relative to other means of generating electricity.
Existing art systems for PV devices may allow for the device to be directly mounted to the building structure or they may fasten the devices to battens, channels or “rails” (“stand-offs)) above the building exterior (e.g. roof deck or exterior cladding). These systems may be complicated, typically do not install like conventional cladding materials (e.g. roofing shingles or siding) and, as a consequence, may be expensive to install. Also, they may not be visually appealing as they do not look like conventional building materials. “Stand-offs” to mount PV device every 2-4 feet may be required. Thus, installation cost can be as much or more as the cost of the article. They also may suffer from issues related to environmental conditions such as warping, fading and degradation of its physical properties.
It is believed that most standard roofing shingles used today are constructed with asphalt cement. This may contain mineral granules and fiberglass matt, but the modulus is suitably low, so as to allow conformity to irregularities on the roof. This material is also designed to allow for bonding between layers of shingles so as to resist wind and weather from penetrating the layers. They offer a high friction surface between their primary materials of construction and the adhesive strips that may be located on the back side.
In developing new shingles or slates with higher durability the materials of construction will change. Specifically in the case of solar shingles, the standard asphalt based materials are not suitable, it may be desirable to construct the shingles, slates, tiles, or solar devices with a polymeric material such as a polyolefin with or without inorganic fillers. This material is low cost, resistant to moisture damage, and may be designed for a multitude of physical properties and colors. Several problems may arise when using these materials due to their low coefficient of friction and ability to be repaired or modified on the roof.
The specific problem of low coefficient of friction may be exacerbated when the roof becomes high pitch (greater than 3:12) and when solar devices are integrated. In these cases, the shingles may slide off the roof during installation if the installer does not take extra caution. This is unlike a standard asphalt shingle that will tack and conform to other sheathing elements and fend to stay in place during installation. The cost, weight, and fragile nature of a solar roofing product may make this problem more critical. Because the solar roofing product may contain fragile materials, such as glass, solar ceils, and electrical connectors, it would most likely be destroyed if it was to slide off the roof. These same materials may also result in higher weights and greater size, making them more difficult to hold on the roof prior to installing.
When high contents of mineral fillers or non-elastomeric polymers are used on the roofing product, it may also be desirable to create a pre-bend in the part, so the bottom edge is forced into the roof deck upon nailing to aid in wind resistance and water sealing. This may make holding the roofing product in its location properly more difficult due to not contacting the roof at the critical nailing point until a nailing force is applied. This can result in the shingle drifting off its desired location until fully nailed in position.
Among the literature that can pertain to this technology include the following patent documents: US20040206035A1; WO2010151777A2; WO2010144226A1; EP2216829A1; and WO1998036139A1, all incorporated herein by reference for all purposes.